This project involves the longtudinal study of a group of 12-year-old rhesus monkeys and two generations of their progeny, all of whom live year-round in a 5-acre enclosure on the grounds of the NIHAC. The 12-year-old adults were all laboratory born, hand-related in a nursery, and subsequently put together as a mixed-sex peer group. Despite the fact that none of these now middle-aged monkeys (nor any of their progeny) have had any physical exposure to any other monkeys, since they were first moved outdoors as juveniles they have consistently exhibited the full compliment of species-normative social behavior and group organization reported to date for rhesus monkeys born and living in fetal environments. The past 12-month period was the first complete annual cycle that the present group had spent entirely in the same outdoor environment since its inception. Not only did all group members successfully adapt to the climatic extremes of the Maryland winter and summer, but also they demonstrated seasonally based changes in foraging patterns, diet, and social behavioral activities, including the emergency of a distinct breeding season (and subsequent birth season), that once again were consistent with existing data from rhesus monkey groups living in feral environments. Furthermore, the observed similarity of the present group's patterns of social organization and demographic dynamics to those of wild groups was extended this past year to include adolescent male peripheralization, with the group expulsion of the first male offspring to approach adulthood. These results serve to reinforce our previous impressions that major portions of rhesus monkey behavioral repertoires have deep-rooted genetic foundations. Additions to and modifications of the subjects' physical environment within the 5-acre enclosure were also completed this past year, and formal designs for a second enclosure and plans for its consitutent monkey group were initiated.